Monday, July 18, 2011

Tropical Storm Bret: July 18, Update B

TS Bret is a very well behaved storm, isn’t he? (well… apart from the sneaking up when I’m not around bit ;-)).

He has been steadily intensifying as expected and now has winds of about 65mph (TS range: 39-73mph) which makes him a strong Tropical Storm. Central pressure is 996mb. He made that North-Northeast turn, also as expected, and is now heading NNE at 7mph so he is moving away from the Bahamas and out into the open ocean. He is currently centered at around 28.5N, 76.8W.

I agree with the NHC track that he will begin to move towards the NE soon (actually, it looks like he is already moving in that direction). He may strengthen a little more, but I am not totally convinced of this and at the moment I don’t see any signs that he will make it to hurricane strength. The only reason he might intensify further is because wind shear is low and will remain low for a few more hours, but there are a few factors working against his intensification. For a start, there is no real circulation in the upper troposphere, which is something we always see with hurricanes. Also, the circulation at the lower levels of the troposphere is not a very well defined circular shape – it’s a bit wibbly-wobbly and elongated. Another factor is that although Sea Surface Temperatures (SSTs) are over 29 deg C, and are therefore warm enough to sustain a storm (need SSTs greater than 26.5 deg C to sustain a storm), the warm water is a very shallow layer at the surface of the ocean so as he churns up the waters underneath, he is pulling up cooler water. If it was warmer with depth, then I’d be a bit more concerned. And finally, he is pulling dry air into the storm, so the convective activity is already decreasing. Here is a NOAA satellite image (infra-red) of the convection across the Western Atlantic, Caribbean, Gulf of Mexico, and Eastern Pacific:

Bret is the yellow/blue blob just north of the Bahamas and east of Florida. The other Tropical Storm on this map is in the Pacific – the red/orange/yellow/blue blobette at around 10N, 95W is TS Dora. Red colours indicate strong thundery weather, yellow is rainfall with little-to-no thunder, and blue is just cloudy no rain. You can see the difference in the amount of convection between the two Tropical Storms… Bret looks a bit wimpy in comparison to Dora (she may become a hurricane in the Pacific within a day or so

I’ll continue to keep an eye on him (to make sure he continues to behave!), but I don’t think he’ll be too much of a bother to anyone (unless you are sailing in that part of the Atlantic… in which case it might be a tad bit rocky). I imagine the surf is not bad along the Florida Atlantic coast though. J

Oh look, it’s ice-cream-o-clock!

Ciao for now,

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These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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